GT-Styrene is Sulzer GTC’s extractive distillation process that directly recovers styrene from the raw pyrolysis gasoline derived from the steam cracking of naphtha, gas oils, and natural gas liquids (NGL).  The styrene, produced at high purities and suitable for polymerization,  is a less costly alternative to conventional styrene production routes.  If desired, the mixed xylenes can also be extracted from the pygas, raising their value as a chemical feedstock.  Our GT-Styrene process is economically attractive to steam cracker operators which produce greater than 500 KMTA ethylene from liquids feedstock.

Process Description

Raw pyrolysis gasoline is prefractionated into a heartcut C8 stream.  The resulting styrene concentrate is fed to an ED column and mixed with a selective solvent, which extracts the styrene to the tower bottoms.  The rich solvent mixture is routed to a solvent recovery column (SRC), which recycles the lean solvent back to the ED column and recovers the styrene overhead.  A final purification step produces a 99.9% styrene product containing less than 50-ppm phenyl acetylene.  The ED column overhead can be further processed to recover a high-quality mixed-xylene stream.  A typical world-scale cracker can produce approximately 25,000 tpy styrene and 75,000 tpy mixed xylenes from pyrolysis gasoline.

Process Advantages

  • Produces polymer-grade styrene at 99.9% purity
  • Allows the recovery of isomer-quality mixed xylenes for paraxylene production
  • Debottlenecks pygas hydrotreater and extends cycle length
  • Reduces hydrogen consumed in hydrotreating
  • Optimized solvent system and design provide economical operating costs